The Magikarp is a water-type Pokemon that evolves into Gyarados at level 20. The Magikarp is considered to be one of the most useless of all Pokemon.
The reason Magikarp is considered to be so useless is because of the limited number of attacks it can learn and the terrible stats it has. However, when the Magikarp reaches level 20, it evolves into the powerful dragon and water-type Pokemon Gyarados, who can use the ultra-powerful Dragon Rage attack to defeat enemies. Finding a Gyarados in the wild is extremely rare, which means that you have to use a Magikarp in battles to get it to evolve. The best strategy is to keep five other strong Pokemon in your party and send your Magikarp out to fight only briefly so that it benefits from gaining experience points earned by more powerful Pokemon.